The invention relates generally to the field of medical science. In particular, but not by way of limitation, the invention relates to a system and method for performing radiotherapy using monochromatic x-ray beams.
Systems and methods are known for performing radiotherapy. For instance, conventional cancer treatments use radiation therapy to deliver a lethal dose of radiation to cancerous tumor tissues and/or the related margin tissue. Radiation therapy can be an attractive alternative to surgery because radiation therapy can be entirely non-invasive. Radiation therapy can be divided into two categories, external beam and brachytherapy. External beam is radiation originating outside the body and aimed at the tumor or object of treatment; brachytherapy is radiation treatment where the radiation source is placed within or adjacent to the site to be treated.
Known methods for delivering external beam radiation have various disadvantages. For example, a significant disadvantage of conventional external beam radiotherapy is the undesirable effect on tissue in non-targeted areas. In an effort to minimize this problem, radiation can be introduced to the body at several different angles—delivering a relatively small amount in each of multiple treatments, with a lethal dose accumulating over many days at the central point of all the projections, the targeted tumor and/or related margin tissue.
Because a tumor presents different profiles and thickness at each angle, methods have been developed to vary the intensity of the beam radiation. This intensity difference can be achieved with longer exposure times and with different radiation intensities. Varying the intensity of the beam at each projection is often referred to as IMRT (Intensity Modulated Radiation Therapy). The use of IMRT has expanded rapidly, adding to the expense and complexity of the delivery systems and the planning of the treatment. Planning the radiation treatment regimen for a patient is a complex process where the numerous angles, beam shape, beam intensity, and number of treatments (fractions) are considered to calculate the minimum dose to the target tissue and the maximum dose allowed to the areas to be spared.
The difficulty of treating a patient in this manner is further complicated by difficulties in assuring that the target tissue being treated is precisely in the path of the radiation beam. This is because the apparatus used for imaging the target tumor or margin tissue is not the same apparatus used for treatment. Patient movements between imaging and treatment can thus change the position of the target tissue with respect to marks placed on the skin, or with respect to bony structures in the patient. Moreover, the size and location of the target tissue can and does change during a course of a treatment that lasts for several weeks. All of these factors contribute to the difficulty in aligning the external radiation beam with the target tissue.
Even where external beam radiation is on target, known systems and methods require high doses of radiation (typically 60-80 Gy) using very high energy x-ray photons in the 4-25 MeV range. The result is a debilitating, lengthy, and difficult process for the patient, commonly causing radiation sickness and/or other temporary or permanent side effects. Moreover, because of the effect of high doses of radiation on neighboring non-target tissue, known radiation treatment cannot be used where the target tissue is proximate to deep organs. For example, use of radiotherapy for treating head and neck tumors, or for treating recurrent skin tumors of the scalp and face, is suboptimal due to the high risk of injury to neural and brain tissues.
Therefore, a need exists for a system and method that simplifies and improves the accuracy of targeting external beam radiation. In addition, a system and method is needed that reduces the amount of external beam radiation energy that is applied to destroy target tissues.